The invention is related to a composite disc rotor for a disc brake of a high-performance vehicle such as racing car and sports car. Specifically, the invention is related to a composite disc rotor capable of reducing a number of parts to thus reduce a cost while securing sufficient durability and reliability.
Since a high force is applied to a disc rotor, which is provided in a disc brake for braking a vehicle, upon braking, it is necessary to secure sufficient strength and rigidity, so that a weight thereof is apt to increase. On one hand, since the disc rotor is provided at a side closer to a road surface than a spring incorporated to a suspension, i.e., with the disc rotor performs as unspring weight, it is required to reduce the weight even if only slightly, for a ride quality or traveling stability. Therefore, a composite disc rotor has been known in which an inner peripheral edge part of a disc main body and an outer peripheral edge part of a coupling bracket referred to as a bell are connected by a plurality of sets of coupling units at a plurality of equally-spaced positions in a circumferential direction so that high brake torque which is applied upon braking can be transmitted (refer to Patent Documents 1 to 5). In addition, the circumferential direction in the present specification means a circumferential direction of the disc rotor, unless particularly mentioned. An axial direction in the specification means an axial direction of the disc rotor, unless particularly mentioned. A radial direction in the specification means a radial direction of the disc rotor, unless particularly mentioned.
In the composite disc rotor, the disc main body is made of a light material having sufficient wear resistance such as ceramic composite material or carbon composite material. Also, as disclosed in Patent Document 1, the disc main body may be formed of cast iron. In any case, entire shape of the disc main body is a circular ring shape, and both side surfaces thereof in the axial direction perform as a pair of friction surfaces to which pads are pushed upon the braking. In addition, the coupling bracket is made of a light alloy such as aluminum-based alloy, magnesium-based alloy and the like and, entire shape of the coupling bracket is a circular ring shape or a circular disc shape having a step portion which is provided at a central portion in the radial direction. The coupling bracket is coupled and fixed to a hub together with a wheel at an assembled state of the disc brake. The hub is a rotating-side bearing ring member consisting of a rolling bearing unit for wheel support. Also, each coupling unit couples the disc main body and the coupling bracket so that the brake torque can be transmitted therebetween and a difference of amounts of thermal expansion and contraction based on temperature changes can be absorbed.
The basic structure of the composite disc rotor is as described above. In the conventional structure disclosed in Patent Documents 1, 2 and 4, however, the number of parts is large, and the cost is increased. In the disc main body and the coupling bracket which are strongly coupled and fixed, the high force is applied to the respective coupling units in addition to the brake torque, due to a moment between the disc main body and the coupling bracket upon the braking. Therefore, it is thus difficult to secure the durability in the structure disclosed in Patent Document 3). Also, since a plate spring having a poor yield of the material thereof is used as the structure disclosed in Patent Document 5, the cost is increased.
[Patent Document 1] JP-A-2004-530848
[Patent Document 2] JP-A-2006-528332
[Patent Document 3] EP 1 013 956 B2
[Patent Document 4] EP 1 930 617 B1
[Patent Document 5] EP 1 970 591 B1